A pulp suspension serving as paper making material, particularly, a pulp suspension composed of waste paper pulp disintegrated by a pulper or the like contains foreign matter such as, for example, resin scrapes and tar grains caused by binding strings, metal foreign matter such as, for example, a metal binding device.
Heretofore, a cyclone apparatus, a vibration apparatus, a centrifugal separator or the like has been used as an apparatus for obtaining a refined paper material by removing foreign matter from the pulp suspension.
On the other hand, a patent material 1 owned by the present applicant provides a drum type washing apparatus, in which a pulp suspension is fed into a rotary drum which is laterally installed, and the pulp suspension thus fed is repeatedly raked up and dropped by a raking fin formed on an inner peripheral surface of the rotary drum, so that the ink component contained in the pulp suspension is filtrated and dehydrated through air and water passing apertures which are formed in the peripheral wall of the rotary drum.
[Patent Material 1] Official Gazette of Japanese Patent No. 3,231,748.